text: const assert = require('assert');
  const SemanticSDP = require('../index');
  
  const MediaInfo = SemanticSDP.MediaInfo;
  
  const capabilities = {
    codecs: ['vp9'],
    rtx: true,
    simulcast: true,
    rtcpfbs: [
      { id: 'goog-remb' },
      { id: 'ccm', params: ['fir'] },
      { id: 'nack' },
      { id: 'nack', params: ['pli'] },
    ],
    extensions: [
      'urn:3gpp:video-orientation',
      'http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01',
      'urn:ietf:params:rtp-hdrext:sdes:mid',
      'urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id',
      'urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id',
      'http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time',
      'test:7',
      'test:8',
      'test:9',
      'test:10',
      'test:11',
      'test:12',
      'test:13',
      'test:14',
      'test:15',
    ],
  };
  
  const media = MediaInfo.create('video', capabilities);
  
  const extensionIds = Array.from(media.extensions.keys());
  
  assert(!extensionIds.includes(0), 'Extension id MUST NOT be 0');
  assert(!extensionIds.includes(15), 'Extension id MUST NOT be 15');
  assert(extensionIds.length === 15, `Expected 15 extensions in total, found ${extensionIds.length}`)